Catheter having optimized balloon taper angle

ABSTRACT

A dilation catheter and expandable balloon. The catheter includes a catheter tube, a proximal end, a distal end and an axis which extends between the proximal and distal ends. A balloon has two ends, at least one end mounts on the distal end of the catheter. The balloon inflates and deflates between a collapsed configuration and an expanded configuration. The balloon has a tapered portion and a working length. The tapered portion extends from the catheter tube at an angle α within the range of 7° to 20° and attaches the working length of the balloon to the catheter tube. Accordingly, the angle α between the tapered portion and the catheter tube is optimized to enable the balloon to slide when the balloon is in the collapsed configuration.

This application is a divisional of copending U.S. Nonprovisional PatentApplication No. 08/698,094, filing date Aug. 15, 1996

CROSS-REFERENCE TO RELATED PATENTS

The present invention relates in subject matter to U.S. Pat. No.4,582,181 (Samson); U.S. Pat. No. 5,350,395 (Yock); U.S. Pat. No.5,242,399 (Lau et al.); U.S. Pat. No. 5,348,545 (Shani et al); U.S. Pat.No. 5,334,154 (Samson et al.) and U.S. Pat. No. 5,480,383 (Bagaoisan etal), The disclosures of these related patents are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to dilation catheters. Moreparticularly, this invention relates to intravascular catheter balloons.

2. Previous Art

Various dilation catheters rely upon an inflatable balloon for applyingpressure against the interior of a biological conduit such as a bloodvessel. These inflatable balloons come in various shapes and sizes toperform any of a number of functions. For example, dilation cathetersare used in percutaneous transluminal coronary angioplasty (PTCA);vascular prosthesis implantation; atherectomy and various other medicalprocedures.

In classical PTCA, a hollow guiding catheter, a guidewire and a dilationcatheter are inserted into the vasculature of a patient. The guidingcatheter has a pre-shaped distal tip which is percutaneously introducedinto the vasculature and advanced. An operator, such as a surgeon,twists and moves the proximal end of the guiding catheter to advance thedistal tip through the aorta. The distal tip reaches the ostium of adiseased coronary artery. An example of a guiding catheter and theoperation thereof is disclosed in U.S. Pat. No. 5,348,545 (Shani et al),the disclosure of which is incorporated herein by reference.

While the distal end of the guiding catheter is seated in the ostium,the guidewire advances out the distal tip of the guiding catheter intothe diseased coronary artery. The operator twists the proximal end ofthe guidewire to guide the curved distal end of the guidewire. Theoperator advances the guidewire within the coronary anatomy until theshaped distal end of the guidewire enters the diseased coronary artery.The diseased artery may include a stenosed region having a lesion, forexample. This advancement of the guidewire continues until the guidewirecrosses a lesion, prosthetic implant or other region to be dilated.

The dilation catheter slides over the guidewire and through the guidingcatheter. The dilation catheter then advances out of the distal tip ofthe guiding catheter, over the previously advanced guidewire until theballoon on the distal end of the dilation catheter is properlypositioned adjacent to the lesion.

Fluid inflates the balloon to a predetermined size. The fluid oftenpressurizes the balloon at pressures which may reach 20 atm but whichare often within the range of 4-12 atm. Conventional balloon designshave two ends attached to the catheter, a working length and a taperedportion. The tapered portion extends between the balloon end and theworking length. Accordingly, the tapered portion defines a transitionbetween the shaft and the balloon end and the working length.

The angle at which tapered portion extends from the catheter istypically greater than 200. The length of the taper (taper length) istypically less than 3 mm.

A variety of dilation catheters exist which may have different purposesincluding prosthetic implantation, angioplasty, atherectomy, diagnosticprocedures and even various re-vascularization techniques which arebeing developed. Rapid exchange and over the wire types of dilationcatheters are two common types of dilation catheters. Examples ofvarious dilation catheters having a balloon are disclosed in U.S. Pat.No. 4,582,181 (Samson); U.S. Pat. No. 5,350,395 (Yock); U.S. Pat. No.5,242,399 (Lau et al.); U.S. Pat. No. 5,334,154 (Samson et al.) and U.S.Pat. No. 5,480,383 (Bagaoisan et al). The disclosures of these patentsare incorporated herein by reference.

Multiple lesions may exist in a diseased coronary artery. It isdesirable to move the deflated balloon across any number of theselesions to optimally position the balloon within the artery forinflation against a selected lesion. With known balloon designs thedeflated balloon may experience considerable frictional force betweenthe balloon and the lesion when the balloon crosses the lesion. Theseare known as cross forces. During withdrawal of the balloon, the balloonmay similarly experiences such frictional forces across the lesion.These forces are known as recross forces. Cross and recross forces aresought to be minimized.

Cross and recross forces may inhibit smooth movement of the deflatedballoon within the vasculature of a patient, cause thrombus buildup, andmay be uncomfortable to the patient. Additionally, if the patent has astent located near the crossed or recrossed lesion, the cross andrecross forces may dislodge the stent. Given that stent implantation isbecoming more common, ways to avoid stent dislodgment are increasinglyimportant considerations for balloon designers.

What is desired is an improved balloon design which more easily crosseslesions while the balloon is deflated. What is also desired is animproved balloon which reduces cross and recross forces.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a balloon which isoptimized to slide within a biological conduit such as a blood vessel.

It is a further object of this invention to provide a balloon having ataper angle which minimizes the cross and recross forces between theballoon and a blood vessel.

In accordance with the above objects and those that will be mentionedand will become apparent below, an apparatus for insertion into abiological conduit, comprises:

a catheter tube having a proximal end, a distal end and an axis whichextends between the proximal and distal ends; and

a balloon, the balloon being mounted on the distal end of the catheter,the balloon expanding from a collapsed configuration to an expandedconfiguration,

the balloon has a tapered portion and a working length, the taperedportion connecting the working length with the catheter tube, thetapered portion extending from the catheter tube at an angle whichremains within the range of 7° and 20 whether the balloon is in anexpanded, collapsed or deformed configuration,

whereby, the angle is optimized to enable the balloon to slide withinthe biological conduit.

In a preferred embodiment, the tapered portion extends from the cathetertube at an angle within the range of 9° and 12°. Preferably, the taperedportion extends from the catheter tube at an angle within the range of10° and 11°.

In another preferred embodiment, the balloon has a taper length withinthe range of 3.0 mm and 9.0 mm. Preferably, the balloon has a taperlength within the range of 5 mm to 7 mm.

In another preferred embodiment, the balloon has a double wall thicknesswithin the range of 1.00-2.00 mm. It can be appreciated that the doublewall thickness is dependent on the material from which the balloon isfabricated. This double wall thickness range is associated with balloonsmade from nylon, PET, and PE, for example. Such materials arecontemplated in various embodiments of the present invention.

In another preferred embodiment, the tubular member includes aninflation lumen extending between the proximal end of the tubular memberand the balloon. The inflation lumen delivers fluid to the balloon toinflate the balloon into the expanded configuration and withdraws fluidfrom the balloon to deflate the balloon into the collapsedconfiguration.

In another preferred embodiment, the tapered portion extends from thecatheter tube at an angle within the range of 9° to 12°. In a variationof this embodiment, the tapered portion extends from the catheter tubeat an angle within the range of 10° to 11°.

In another preferred embodiment, the balloon has a taper length withinthe range of 3.0 to 9.0 mm. In a variation of this embodiment, theballoon has a taper length within the range of 5.0 to 7.0 mm.

An advantage of this invention is to provide a balloon which isoptimized to slide within a biological conduit such as a blood vessel. Afurther advantage of this invention is to provide a balloon having ataper angle which minimizes cross-recross forces experienced by theballoon, whether the balloon is inflated, deflated or deformed.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the objects and advantages of the presentinvention, reference should be had to the following detaileddescription, taken in conjunction with the accompanying drawing, inwhich like parts are given like reference numerals and wherein:

FIG. 1 is a perspective view of an angioplasty catheter having a balloonin accordance with the present invention.

FIG. 2 is a perspective view of an atherectomy catheter in accordancewith the present invention.

FIGS. 3a-3 c are cross-sectional views of insertion of the angioplastycatheter of FIG. 1 into a biological conduit.

FIG. 4 is an enlarged partially cut away perspective view of theangioplasty catheter of FIG. 1 in a biological conduit with the balloonin the expanded configuration.

FIG. 5 is a cross-sectional view of the balloon of FIG. 3c as seen alongthe line 5—5 in the direction of the arrows.

FIG. 6 is an enlarged cross-sectional view of the tapered portion of theballoon of FIG. 5 as encircled by the circle 6.

FIG. 7 is a graphic representation of the relationship of double wallthickness and optimum taper length.

FIG. 8 is an enlarged cross-sectional view of a variation of balloon ofFIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with respect to FIG. 1, whichillustrates a balloon dilation catheter in accordance with the presentinvention, shown generally by the reference numeral 10. The catheter 10has a proximal end 12, a distal end 14, an axis 16 and a catheter tube18. The catheter tube 18 extends between the ends 12 and 14 along theaxis 16.

A balloon 20 mounts on the distal end 14 of the catheter 10. The balloon20 has a proximal end 22 and a distal end 24. The ends 22 and 24 of theballoon 20 parallel the catheter axis 16. The balloon 20 is inflatableto expand from a collapsed configuration to an expanded configuration.The balloon 20 is deflatable after inflation to selectively return tothe collapsed configuration.

The balloon 20 is fabricated from a flexible polymer such as nylon, PET,PE, etc. The balloon 20 has ends 22 and 24. In one embodiment, the ends22 and 24 are formed integrally with the catheter tube 18. In anotherembodiment, the end 22 includes a balloon shaft 19 which bonds to thecatheter tube 18 by adhesive or heat bonding. Examples of cathetershaving a balloon 20 are disclosed in U.S. Pat. No. 4,582,181 (Samson);U.S. Pat. No. 5,350,395 (Yock); U.S. Pat. No. 5,334,154 (Samson et al.)and U.S. Pat. No. 5,480,383 (Bagaoisan et al). The disclosures of thesepatents are incorporated herein by reference.

The catheter 10 is adapted for percutaneous transluminal coronaryangioplasty procedures (PTCA). Although the catheter 10 is adapted forPTCA, it can be appreciated that a balloon in accordance with thepresent invention can be used in conjunction with many other proceduresincluding the implantation and repair of intraluminal (e.g.intravascular) prostheses. An example of a dilation catheter forrepairing an intravascular prosthesis is disclosed in U.S. Pat. No.5,242,399 (Lau et al.), the disclosure of which is incorporated hereinby reference. The Lau patent discloses a dilation catheter fordelivering an intravascular prosthesis to an occluded region of thevasculature of a patient.

It can be appreciated that the balloon 20 and catheter 10 of the presentinvention have multiple applications. Such applications includediagnostic procedures such as cardiological and vascular imaging. Otheruses include laser and mechanical ablation of biological tissue,transluminal medication delivery, and various other interventional,diagnostic and corrective procedures.

With particular reference to FIG. 2, there is shown an atherectomycatheter 30 in accordance with the present invention. The catheter 30includes a catheter tube 18; a work element housing 32 attached to thecatheter tube 18; a balloon 38 attached to the housing 32; a window 34formed in the housing 32; and a work element 36 disposed within thehousing 32. The window 34 exposes the work element 36.

The balloon 38 of the catheter 30 performs multiple functions. Theballoon 38 holds the work element 36 in a desired position within thecardiovascular system. Additional possible uses of a balloon includeholding and repositioning a work element 36 within a biological conduit.It can be appreciated that the work element 36 may include tools inaddition to the atherectomy cutter. The work element 36 may have animaging device, or a drug delivery system, for example.

The balloon 38 mounts on a lateral side of the housing 38, opposing thewindow. In operation, the balloon 38 is normally collapsed duringinsertion of the catheter 30 into a biological conduit. However, whenthe catheter 30 is positioned as desired with the biological conduit,the balloon 38 inflates and expands to hold the distal end of thecatheter 30 in a desired position within the biological conduit. Theballoon 38 adjusts the position of the housing 32 with respect to thebiological conduit.

The catheter tube 18 includes an inflation lumen 42 extending betweenthe proximal end 12 of the catheter 30 and the balloon 38. The inflationlumen 42 delivers fluid to the balloon 38 to inflate the balloon 38 intothe expanded configuration. An example of an atherectomy catheter havingan inflatable balloon is disclosed in U.S. Pat. No. 5,429,136 to Milo etal., the disclosure of which is incorporated herein by reference.

With particular reference to FIGS. 3a-3 c, there is shown the distal end14 of the angioplasty catheter 10 inserting into a blood vessel 46. Thedistal end 14 inserts in stages as will be described with respect toFIGS. 3a, 3 b, and 3 c, respectively.

In FIG. 3a, the balloon 20 is collapsed, having an optimal profile forinsertion into the blood vessel 46. When the balloon 20 collapses, theballoon 20 assumes a flattened configuration and curls around the distalend 14. The balloon 20 remains flattened and curled upon entry into theblood vessel 46. During insertion, the balloon 20 will typically remaingenerally flat and curled, however, after inflation at high pressures,the balloon 20 and may fold or form surface wrinkles.

The collapsed balloon has lateral edges 55 which curl and stay curled asthe balloon 20 inserts through the blood vessel 46. With the edges 55curled, the balloon 20 attains a generally tubular configuration. It canbe appreciated that the edges 55 uncurl as the balloon 20 inflates.

While the balloon 20 is collapsed, the lateral edges 55 define the taperangle α which extends from the balloon shaft 19. The edges 55 aredefined on the proximal end 22 and the distal end 24 of the balloon 20.The taper angle α minimizes friction between the balloon 20 and theblood vessel 46. The taper angle α eases insertion of the catheter 10through the blood vessel 46.

In the second stage, shown particularly by FIG. 3b, the balloon 20inserts into the blood vessel 46 and inflates. Inflation of the balloon20 expands the inside diameter (ID) 54 of the blood vessel 46 at thesitus of the lesion 50. The balloon 20 holds the distal end 24 of thecatheter in the blood vessel 46. The balloon 20 also compresses thelesion 50 against the ID 54 of the blood vessel 46. Compression of thelesion optimally restores normal blood flow through the blood vessel 46.It can be appreciated, however, that in other aspects of the invention,the balloon 20 may be adapted for inserting and expanding anintraluminal prosthesis, to hold a medical device within a lumen, orother purposes.

As shown in FIG. 3c, and after compression of the lesion 50, the balloon20 deflates into the collapsed configuration. The balloon 20 ideallywill deflate and the edges of the balloon will curl the balloon 20 intoa cylindrical shape as shown in FIG. 3a. Often, however, the balloon 20will deform as shown. Deformation of the balloon is typically due tohigh pressures experienced during inflation (e.g. 10-20 atm.). Thedeformed balloon 20 has a flat portion which is generally flat and theedges may curl less than shown in FIG. 3a.

The taper angle α is optimized to enable the deformed balloon 20 to movethrough the blood vessel 46 with minimal force. Accordingly, the balloon20 may further insert through the blood vessel 46 to the next lesion 51.The process of expanding the inside diameter (ID) 54 repeats at the siteof the lesion 51.

Reciprocally moving the catheter 10 across lesions causes frictionalforces between the lesion 51 and the balloon 20. These frictional forcesare termed cross-recross (CRC) forces. The taper angle α is optimized tominimize the cross-recross forces when the balloon 20 is in thecollapsed configuration whether the balloon is deformed or not. Thetaper angle α as measured when the balloon 20 is in the collapsedconfiguration is the approximately the same angle as measured when theballoon 20 is expanded, collapsed or deformed. Although the taper angleα is optimized to reduce CRC forces when the balloon crosses a lesion,it can be appreciated that the taper angle α also has the effect ofreducing friction between healthy portions of a blood vessel and theballoon 20. The taper angle ca is maintained while the balloon 20expands and collapses.

The terms “collapsed” and “collapsed configuration” indicate that theballoon 20 is not fully expanded. The collapsed balloon 20 holds avolume of fluid which is significantly less than the volume of fluidheld by the balloon 20 when expanded. A typical expanded balloon 20 mayhold pressure of 10-20 atm, for example. A collapsed balloon may holdpressure of less than 1 atm. It can be appreciated that the pressures atwhich the balloon inflates and deflates may vary in accordance with theparticular catheter and balloon design requirements.

With particular reference to FIG. 4, there is shown the balloon 20 ofFIG. 1 inserted into the blood vessel 46 and inflated to expand theinside diameter 54 (ID) of the blood vessel 46 at the location of thelesion 50. Expanding the ID 54 of the blood vessel 46 facilitatesimproved blood flow through the blood vessel after the catheter 10 isremoved.

The balloon 20 has a working length 60 which is defined between theballoon ends 22 and 24. The ends 22 and 24 are generally symmetrical inshape. The balloon 20 has a tapered portion 62 which extends betweeneach end 22 and 24. The tapered portion 62 is formed integral with theworking length 60, and the catheter tube 18. The tapered portion 62 andthe catheter tube 18 meet to form the taper angle α.

With particular reference to FIG. 5, there is shown the collapsedballoon 20 of FIG. 3c in cross-section as seen facing a flat portion ofthe balloon 20. The distal end 14 of the catheter tube 18 abuts theballoon shaft 19. The tapered portion 62 defines a taper length 66. Thetaper length 66 extends a distance “I”. In one embodiment, the distance“I” is within the range of 3 mm to 9 mm. In another embodiment, thedistance “I” is within the range of 5 mm to 7 mm. The distance “I” ismeasured parallel to the catheter axis 16.

The working length 60 of the balloon 20 has a generally uniform radius56. The radius 56 extends between the axis 16 and the working length 60.During use, the working length 60 applies radial pressure to the insidediameter of the blood vessel when the balloon 20 is in the expandedconfiguration. In one embodiment, the working length 60 has a generallycylindrical shape when the balloon 20 is in the expanded configuration.It can be appreciated, however, that the shape of the working length 60can be adapted to any shape suitable for the desired purpose of theballoon 20.

The tapered portion extends from the catheter tube 18 at the taper angleα. The taper angle α is between 7° and 20°. According to one aspect ofthe invention, the taper angle α is between 9° and 12°. According toanother aspect of the invention, the taper angle α is between 10° and11°.

With particular reference to FIG. 6, there is shown an expanded view ofthe tapered portion 62 of the balloon 20 of FIG. 5. The tapered portion62 is encircled by the circle 6 in FIG. 5. The angle α is the angle atwhich the tapered portion 62 extends from the balloon shaft 19. Theangle β indicates the angle at which the tapered portion 62 meets theworking length 60. According to one aspect of the invention, the anglesα and β are equivalent angles and the working length 60 parallels thecatheter tube 18.

The balloon shaft 19 has a thickness 72. The working length 66 has athickness 74. The thickness 72 of the catheter tube 18 is greater thanthe thickness 74 of the working length 60. The tapered portion 62 tapersfrom the balloon shaft 19 to the working length 60.

When the balloon 20 is in the collapsed configuration the balloon 20double wall thickness (DWT) may be measured. The DWT of the balloon isdefined and calculated to be average double the thickness 72 of theworking length. Preferably, the DWT is within the range of 1.0 mils to1.4 mils as shown in FIG. 7 and depends on the material which theballoon 20 is made from. The DWT is generally measured by a snap gaugeapplied across the flat portion of a collapsed balloon.

With particular reference to FIG. 7, there is shown a diagram of aquadratic model for cross-recross forces generally designated with thereference numeral 80. It is known that the double wall thickness is afactor in determining optimal taper length. An example of an optimumtaper angle line quadratic model for cross-recross forces at 18 atmballoon inflation pressure. Taper length and double wall thickness arerelated to the CRC forces. Accordingly, the optimum taper length isdirectly related to the balloon DWT. The optimum taper length is shownwith reference numeral 82

With particular reference to FIG. 8, there is shown a variation of theballoon 20 of FIG. 1. The balloon 20 has a rounded cross-section with avaried radius 58. The tapered portion 62 defines an arc between theballoon shaft 19 and the working length 60. The tapered portion 62 hasan average slope. The taper angle α equals the average slope of thetapered portion 62. The average slope is depicted by the dotted line 70.The working length 60 extends between the arrows 74.

While the foregoing detailed description has described severalembodiments of the balloon 20 in accordance with this invention, it isto be understood that the above description is illustrative only and notlimiting of the disclosed invention. The balloon 20 may be used in anynumber of devices.

The working length may connect with the catheter tube in a number ofways which are included within the scope of the claims. On way includesusing an intermediary member such as a balloon shaft attached to atleast one end of the balloon and which connects to the catheter tube. Inthis variation, the balloon shaft functions as an intermediary toconnect the tapered portion with the catheter tube.

It will be appreciated that the embodiments discussed above and thevirtually infinite embodiments that are not mentioned could easily bewithin the scope and spirit of this invention. Thus, the invention is tobe limited only by the claims as set forth below.

What is claimed is:
 1. A balloon dilation catheter for use in a bloodvessel having a lesion, comprising: a catheter tube having an axis; aballoon disposed about a portion of the catheter tube, the balloonhaving two ends and a working length therebetween, each end including atapered portion, each tapered portion being attached to the cathetertube, the balloon being inflatable from a collapsed conformation,wherein the working length and at least a portion of each taperedportion are substantially flattened, to an inflated conformation; atapered portion of the balloon in the collapsed conformation defining anedge, the edge defining an acute angle relative to the axis of thecatheter tube; the same tapered portion of the balloon in the inflatedconformation defining an acute angle relative to the axis of thecatheter tube, the angle being of substantially the same measure as thatdefined by the edge when the balloon is in the collapsed conformation.2. A balloon dilation catheter as set forth in claim 1, wherein aportion of the working length and a portion of each taper of the balloonin the collapsed conformation are curled and the curled portions becomeuncurled when the balloon is in the inflated conformation, whereby thetaper angles are maintained at constant measure during inflation anddeflation of the balloon.
 3. A balloon dilation catheter as set forth inclaim 1, wherein the edge defines an angle measuring between 7° and 20°relative to the axis of the catheter tube.
 4. A balloon dilationcatheter as set forth in claim 1, wherein the edge defines an anglemeasuring between 9° and 12° relative to the axis of the catheter tube.5. A balloon dilation catheter as set forth in claim 1, wherein the edgedefines an angle measuring between 10° and 11° relative to the axis ofthe catheter tube.